In Dunn v. United States (1978), the U.S Supreme Court ruled on a case involving the interpretation of "reasonable doubt" in criminal cases. The defendant, Dunn, was convicted for illegal possession and transportation of untaxed whiskey based on circumstantial evidence. He appealed his conviction arguing that jury instructions given by trial judge were incorrect because they equated reasonable doubt with substantial doubt and grave uncertainty which he argued raised the government's burden of proof higher than required by law. The Supreme Court held that while it is preferable to avoid equating 'reasonable doubt' with terms like 'substantial or grave uncertainty', such an instruction does not necessarily render a trial fundamentally unfair or unreliable as long as taken as a whole, it correctly conveyed the concept of reasonable doubt to jurors. Therefore, even if some parts may be potentially misleading when viewed in isolation, what matters is whether there was any likelihood that jurors misunderstood their role due to these instructions. Thus, despite agreeing with Dunn’s argument about potential confusion arising from using certain phrases interchangeably with ‘reasonable doubt’, his conviction was upheld since overall understanding imparted by those instructions did not violate due process rights.

In the dissenting opinion for Dunn v. United States, Justice Thurgood Marshall argued that the majority's decision undermined a fundamental principle of criminal law: that defendants should only be convicted based on proof beyond a reasonable doubt. He criticized the Court's ruling as allowing juries to convict without fully understanding or agreeing upon which specific acts constituted the crime charged. In this case, he believed there was no way to determine whether all jurors agreed about which two acts formed part of Dunn’s continuous criminal behavior - an essential element in proving his guilt under federal law. Therefore, according to Marshall, it could not be said with certainty that Dunn had been found guilty beyond a reasonable doubt and his conviction should have been overturned.